  /* 论坛页面顶部导航栏样式 */
        .header {
            background: var(--card-bg);
            box-shadow: var(--shadow);
            padding: 18px 30px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            border-radius: 12px;
            margin-bottom: 30px;
            color:  #4a6cf7;
        }

        .top-nav {
            display: flex;
            gap: 60px;
            color:  #4a6cf7;
        }

        .top-nav a {
            text-decoration: none;
            color: var(--text-primary);
            font-weight: 500;
            font-size: 16px;
            transition: color 0.2s;
            position: relative;
        }

        .top-nav a:hover {
            color: var(--primary-color);
        }

        .top-nav a.active {
            color: var(--primary-color);
        }

        .top-nav a.active::after {
            content: '';
            position: absolute;
            bottom: -5px;
            left: 0;
            width: 100%;
            height: 3px;
            background: var(--gradient);
            border-radius: 2px;
        }

        .auth-buttons {
            display: flex;
            gap: 15px;
            align-items: center;
        }
